Answer:
Each cell has a unique chemical composition
Explanation:
All the other answers are apart of the modern cell theory.
There is no defined limit on the capacity of the brain. The brain's capacity cannot be measured as it is not subject to a defined "space" where the memory is kept, and it is not such that each neuron is responsible for a single memory. The brain has complex mechanisms of memory storage, that even improve if trained.
The central nervous system by sending messages from the brain through the nerves that go to your spine.
Happy St. Patrick’s day too!